Insides of an A8 Muffler
06-20-2007, 03:55 AM
#1
New Member
Thread Starter
Join Date: May 2002
Posts: 182
Likes: 0
Received 0 Likes
on
0 Posts
Insides of an A8 Muffler
I met with A8drifter two weeks ago and he gave me some misc. parts that he was getting rid of which was very generous of him. One of the items that I was interested in was his old muffler. I was contemplating modifying it to have a diverter valve so that I could bypass it when I wanted a little more rumble from the exhaust system.
After I cut it open and removed all the fiberglass sound deadening I found a very interesting pipe arrangement. As you can see in the pictures one pipe is basically a straight though configuration and the other pipe is much longer. The longer pipe would be on the driver's side since the muffler is shown upside down. I really can't think of a good reason to make this one pipe so much longer than the other.
It looks like it would be very difficult to install a diverter valve so I think at this point I might just weld it shut without the fiberglass insulation and see how it sounds. Anyone have any thoughts on this.
Jeff B
<img src="http://pictureposter.audiworld.com/36855/muffler_1.jpg">
<img src="http://pictureposter.audiworld.com/36855/muffler_2.jpg">
After I cut it open and removed all the fiberglass sound deadening I found a very interesting pipe arrangement. As you can see in the pictures one pipe is basically a straight though configuration and the other pipe is much longer. The longer pipe would be on the driver's side since the muffler is shown upside down. I really can't think of a good reason to make this one pipe so much longer than the other.
It looks like it would be very difficult to install a diverter valve so I think at this point I might just weld it shut without the fiberglass insulation and see how it sounds. Anyone have any thoughts on this.
Jeff B
<img src="http://pictureposter.audiworld.com/36855/muffler_1.jpg">
<img src="http://pictureposter.audiworld.com/36855/muffler_2.jpg">
06-20-2007, 04:20 AM
#2
Elder Member
Join Date: Mar 2001
Posts: 11,968
Likes: 0
Received 0 Likes
on
0 Posts
The different lengths would resonate at different frequencies.
Each would tend to "drone" at a different frequency, and at half the loudness, compared to a muffler with equal length internals. The result is probably a subjective improvement in the quality of the exhaust note.
On the negative side, the two 180o switchbacks in the long run would add significant pressure drop and reduce the HP produced by the driver's side bank of the V8 :-(
And just to confirm: This is the muffler at the rear, not the resonator in the center?
And thanks for posting the pic ... fascinating.
On the negative side, the two 180o switchbacks in the long run would add significant pressure drop and reduce the HP produced by the driver's side bank of the V8 :-(
And just to confirm: This is the muffler at the rear, not the resonator in the center?
And thanks for posting the pic ... fascinating.
06-20-2007, 05:03 AM
#3
New Member
Thread Starter
Join Date: May 2002
Posts: 182
Likes: 0
Received 0 Likes
on
0 Posts
Re: The different lengths would resonate at different frequencies.
I would agree that it might be different lengths for sound tuning. I am just surprised that they would put that much more restriction on the driver's side cylinder bank.
You are correct that it is the back muffler.
Jeff B
You are correct that it is the back muffler.
Jeff B
06-20-2007, 05:23 AM
#4
AudiWorld Super User
So how does it work?
Exhaust gas enters from one side, and then exits out the other side.
In the actual muffler there are a lot of little holes in the pipe. Are the pipes still through pipes with just holes drilled in them? If so, how does this muffle the sound.
Just curious, never seen this before.
Remember, there is a "H" pipe that cross connects the two pipes in parallel.
In the actual muffler there are a lot of little holes in the pipe. Are the pipes still through pipes with just holes drilled in them? If so, how does this muffle the sound.
Just curious, never seen this before.
Remember, there is a "H" pipe that cross connects the two pipes in parallel.
06-20-2007, 05:45 AM
#5
Its pretty meticulous with the perforation....the pattern isn't a random perf. If you look
on the longer one, near the exhaust tip, it juts out and steps in on the pattern of the perforation.
I'm sure Audi engineers fine tuned it in the end...but to what degree? Wow, D2s surprise me everyday! I really miss the ol girl.
I'm sure Audi engineers fine tuned it in the end...but to what degree? Wow, D2s surprise me everyday! I really miss the ol girl.
06-20-2007, 05:47 AM
#6
I'll bet the fiberglass soaks up the sound a lot....it will probably be quieter than my straight
pipe and louder than stock....can't sound too harsh considering I had just a straight pipe and it sounded SWEEEET!
06-20-2007, 05:57 AM
#7
AudiWorld Super User
Join Date: Jan 2005
Posts: 2,564
Likes: 0
Received 0 Likes
on
0 Posts
And this beggggggggggggggs the penultimate question:
Anyone care to postulate the identity of the innards of der //S8 rear box? Tink it be da same?
Jeff... please report back your findings of the effect of removing the glasspack.
Interesting stuff, definitely.
Car's too damn quiet! But I don't want a Chevelle SS either. Local guy's V8Q with Stebro while sounded kinda neat was a bit over the top for me tastes.
Bueller?
Jeff... please report back your findings of the effect of removing the glasspack.
Interesting stuff, definitely.
Car's too damn quiet! But I don't want a Chevelle SS either. Local guy's V8Q with Stebro while sounded kinda neat was a bit over the top for me tastes.
Bueller?
Trending Topics
06-20-2007, 05:59 AM
#8
New Member
Thread Starter
Join Date: May 2002
Posts: 182
Likes: 0
Received 0 Likes
on
0 Posts
Re: So how does it work?
The way it works is that the sound escapes out of the holes that are in the pipe and the fiberglass material absorbs it.
The sections of the pipe that have the holes are wrapped with a steel wool type of material that is about a ¼ inch thick. You can see this material on the far right chamber of the muffler since I didn't remove it from the pipe yet. This steel wool material keeps the finer fiberglass stuffing from escaping out of the holes in the pipe. As the sound waves exit the holes in the pipe they are absorbed by the fiberglass material.
Jeff B
The sections of the pipe that have the holes are wrapped with a steel wool type of material that is about a ¼ inch thick. You can see this material on the far right chamber of the muffler since I didn't remove it from the pipe yet. This steel wool material keeps the finer fiberglass stuffing from escaping out of the holes in the pipe. As the sound waves exit the holes in the pipe they are absorbed by the fiberglass material.
Jeff B
06-20-2007, 06:43 AM
#9
glass pack removal
I would think with the fiberglass removed the muffler casing would "ring" at a frequency that some might find annoying. With all those small holes you have to think of the muffler as a sonic bladder, expanding ever so slightly to absorb the sound pulses. It would be interesting to know what's is inside the resonator. I suspect that's where the major restrictions are because, sonicly speaking, it's important to cancel the noise as close to the source as possible.